The tergites, or chitinized dorsal halves of the body rings, are fused to form a " prosomatic carapace," or carapace of the prosoma, in both Limulus and Scorpio (see figs, 7 and 8).
The tergites of this region and those of the following region, the metasoma, are fused to form a second or posterior carapace in Limulus, whilst remaining free in Scorpio.
A telsonic tergal shield of greater or less size is always present, which may be imperfectly divided into well-marked but immovable tergites indicating incompletely differentiated somites.
On the other hand, it may well be doubted whether the pygidial or posterior carapace is primarily due to a fusion of the tergites of somites which were previously movable and well developed.
58); 5, the fifth, and 11, the eleventh tergites of the opisthosoma; pa, the conical post-anal lobe.
I to VI, the prosomatic appendages; 4, 5, 6, the fourth, fifth and sixth tergites of the opisthosoma.